This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project is one of four projects in a program project grant entitled "Combined Approach to Broadly Protective AIDS Vaccine." Project 1 (Overbaugh) seeks to identify non-subtype B viruses that have biological and immunological properties suitable for vaccine development. Project 2 (Haigwood) seeks to generate broadly neutralizing antibodies (NAbs) by "quasispecies" envelope vaccines. Project 3 (Stamatatos) seeks to examine Envelope modifications as an approach to elicit broad NAbs, and Project 4 (Hu and Kaja) will analyze and refine the "prime-boost" strategy to augment both T and B cell responses against SHIV in nonhuman primates. In Project 2 (Dual Subtype Quasispecies Envelope SHIV Vaccine), individual env genes are tested as DNA and protein vaccines in rabbits. We hypothesize that exposure to the gradually changing natural Envelopes encoded by the DNA vaccines will elicit qualitatively different responses than clonal or mixtures of Envelopes.